Johnson says he was diagnosed with a kidney disease at age 25 and was told his kidneys would shut down within a couple of years. In fact, he says, he took care of himself and has not required dialysis, even 31 years later. Now, however, he says, he is on a waiting list for a kidney transplant at Rush University Medical Center.

“Ironically, the way I found out about it was when I took the test to become a police officer,” Johnson recalled. “The testing came back, which led me to go see a kidney specialist.”

Once he has a transplant, he would be able to return to work within a couple of months, Johnson says.

Johnson says he has been upfront with Mayor Emanuel about his health. Emanuel tapped him last year to head the embattled Chicago Police Department.

“He’s exactly the person we want, at exactly this time for the city of Chicago,” Emanuel, standing next to Johnson, said.